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  1. I like the piecewise linear with constraint graph. I suspect that if you move the breakpoint about you will find that the 1997.7 date is a pretty good choice to maximise the difference between the two trends.

    Given that the long term trend increases if we include the post-1997 data, what we are actually seeing is a bump around 1998. In my HadCRUT4 analysis post I attempted to analyse the effect of coverage bias by latitude band using a couple of methods.

    The most notable result is that the poor Arctic and Antarctic coverage both contribute to a peak in warm bias around 1998, declining to a cool bias today. It’s not up to peer review standards and it would be interesting for someone who knows more about reanalysis to have a look at it from that perspective, but the results are at least suggestive.

    One interesting question is how this squares with Foster and Rahmstorf. They get a linear result without correcting for coverage bias. If I’m right about the coverage bias, then they must be mopping up the coverage bias in the other three terms.

    Comment by Kevin C — 1 Nov 2012 @ 5:54 AM

  2. Good stuff as usual. If you just look at your first graph, the decadal means look pretty convincing to me on their own.Just by eye, they seem to fit the Aug 1975-Aug 2012 line pretty well.

    Comment by Philip Machanick — 1 Nov 2012 @ 6:23 AM

  3. As usual, a very nice presentation of the issue.

    One minor request, could you attach a number to each of the figures for ease of reference for the posters here?

    On larger question–aren’t all attempts to predict the future based merely on lines on graphs from the past what is called ‘curve fitting’–generally not considered a very reliable method?

    Shouldn’t the emphasis always be on the underlying physics and dynamics that might explain both historical trends and possible future developments?

    [Response:Extrapolation into the future, based on past trends, is in fact highly reliable if you have strong reason to believe that the underlying physical drivers of the system under study are not going to change. With climate change of course, we have no such confidence, because of the enormous and rapid increase in GHGs, whose physical basis as a radiative forcing agent is well understand, and quantified. Thus the importance of GCMs, which incorporate this understanding, and also attempt to integrate it with other possible forcings as well as shorter term variations.--Jim]

    Thanks again for a clear and compelling piece.

    Comment by wili — 1 Nov 2012 @ 7:42 AM

  4. Very useful! A slight typo, 1st para below the 1st graph: “…in that there derivation…”

    [Response:Fixed. Thanks - gavin]

    Comment by Kevin McKinney — 1 Nov 2012 @ 9:09 AM

  5. Response to Willi @ 3: “[A]ren’t all attempts to predict the future based merely on lines on graphs from the past what is called ‘curve fitting’…?” No. The emphasis is on the underlying physics and dynamics that explain both historical trends and possible future developments. Get yourself a copy of “Challenges of climate modeling” by Inez Fung in the Journal of theAmericanInstitute of Mathematical Sciences. It’s a good concise description of climate modeling.

    Comment by Jat Dee Are — 1 Nov 2012 @ 10:25 AM

  6. Thanks for pointing out the fact that different statements about the same data can be true at the same time, and that there is a disconnect between a graph and reality when that graph shows a discontinuity in energy state. Apart from microscopic quantum effects, it simply isn’t physically possible for the earth to transition between two disparate energy states with no states in between. That puts such graphs firmly in the realm of mathturbation.

    I’m not sure how you imposed the connected constraint. I assume that the line segments must be calculated using time periods that overlap the preceding one by half the length of one being created. That would be not that different from a running average. Illustration:

    http://www.woodfortrees.org/plot/hadcrut4gl/mean:12/plot/hadcrut4gl/mean:180/plot/hadcrut4gl/from:1997.75/trend/plot/esrl-co2/mean:12/normalise

    Comment by Chris G — 1 Nov 2012 @ 11:02 AM

  7. I assert that recently, more of the heat in the atmosphere has gone into warming the oceans and warming/melting ice. Thus, today, we have warmer ice, warmer oceans, and relatively cooler air. Further, air temperatures do not capture the latent heat in the atmosphere, and the latent heat in the atmosphere has increased.

    My point is that for periods as short as a decade, air temperatures are not a precise measure of the heat in the climate system. And, it is the total heat in the system that drives weather.

    The curves above are for educational purposes only and should not be used for engineering or policy making. If the above are the best data available (and they may be), then safety factors should be applied. The above are not a basis for engineering design.

    Comment by Aaron Lewis — 1 Nov 2012 @ 12:05 PM

  8. Thank you. Calm and clear. And simple enough even for me.

    (The solid green line seems to stick out well past July 1997 before it turns into a dotted line? Is it plotted correctly?)

    Comment by Roddy Campbell — 1 Nov 2012 @ 12:09 PM

  9. These kinds of issues are routinely faced by many other disciplines, which climate scientists should draw upon – economics, demographics, sociology, etc. Whenever you get a time series, especially one that involves human action, there are a wide range of complex statistical issues and complex attempts to address them. These have been explored in millions of studies. With a few exceptions, climate scientists ignore this expertise and analyze trends in a simplistic manner.

    [Response:There is no basis for this last statement. In general, physics (upon which climate science is very largely based) has done as good, or better, of a job at tying underlying physical drivers to observed phenomena, as has any other branch of science, right up there with chemists and molecular biologists. And there are good reasons for why this is so.--Jim]

    Comment by T Marvell — 1 Nov 2012 @ 12:37 PM

  10. Roddy at 8…Looks to me like the dotted line begins at the solid black vertical line denoting August ’97, creating the illusion that it’s a continuation of the solid line from the prior period.

    [Response: yes. - gavin]

    Comment by Walter Pearce — 1 Nov 2012 @ 12:49 PM

  11. Walter at 10 (and Gavin’s confirmation) – I thought of that and zoomed in on that section of the graph – the gaps between the dotted sections are quite big, too big to get lost in that particular junction I think?

    Comment by Roddy Campbell — 1 Nov 2012 @ 1:45 PM

  12. Using HadCRUT4 and a nice set of cherry picked years in combination with the logic of Rose et al, you could proof with trends that the world hasn’t warmed at all since 1957. Trends correctly rounded down in °C/decade:
    1957 – 1986 : 0.02
    1987 – 1996 : 0.02
    1997 – now : 0.04
    According to Rose global warming has stopped in this last period of 16 years and the two preceding periods have trends that are almost close to zero. So three periods of no global warming since 1957 and the overall conclusion, using the correct skeptic logic + statistics, is that the world of 2012 is as warm is the world in the 1950′s.
    Using the catchphrase of the great philosopher Obelix: “These skeptics are crazy!”.

    http://www.woodfortrees.org/plot/hadcrut4gl/from:1957/to:1987/plot/hadcrut4gl/from:1957/to:1987/trend
    http://www.woodfortrees.org/plot/hadcrut4gl/from:1987/to:1997/plot/hadcrut4gl/from:1987/to:1997/trend
    http://www.woodfortrees.org/plot/hadcrut4gl/from:1997/to:2012.6/plot/hadcrut4gl/from:1997/to:2012.6/trend
    http://en.wikipedia.org/wiki/Obelix

    Comment by Jos Hagelaars — 1 Nov 2012 @ 2:57 PM

  13. Response:Extrapolation into the future, based on past trends, is in fact highly reliable if you have strong reason to believe that the underlying physical drivers of the system under study are not going to change (Jim)

    Here is an extrapolation into the future based on the 3 CET constituent harmonic components + the existing linear trend:
    http://www.vukcevic.talktalk.net/CET-NV.htm
    As it happens the multi-decadal trends closely follow the geological non-climatic based records (North Atlantic Precursor) confirming the primacy of the natural variability.

    Comment by vukcevic — 1 Nov 2012 @ 2:58 PM

  14. Good article overall. A couple comments.

    1. Picking a starting point in the graphs at 1980 is just asking for a beating from skeptics for obvious reasons. I will refrain here as we have all been down this well worn path.

    2. “we can also see that the actual temperatures are still within the model envelope (2012 data included to date)”. Although you qualify this in the next sentence, this is indeed misleading IMO. When a very large percentage of the simulations are over estimating temperature versus observations, this should require one to question the validity of these simulations *** out loud ***.

    3. And the big picture. The simulations leading to possible dangerous climate change are contingent upon an accelerating temperature profile in response to BAU carbon output. When the temperature profile is decelerating, this warrants real discussion on the bigger picture, particularly whether climate sensitivities are too high in the models. This seems to be the “theory that shall not be named”. One has to consider the opposite condition, if all the simulations were under-estimating temperatures, would there not be rampant speculation that climate sensitivities were too low?

    [Response: Probably, but that would not be justified either. There is no question that the current situation is the lower part of the model distribution in temperature, but it is not yet inconsistent, and given that the ENSO corrected trends are still very much within the fold, my forecast is that it won't prove to be. Remember that sensitivity is not defined from the models, but from the paleo-climate observations, and so you would need some radical departure from expected behaviour to challenge that. We are nowhere close. - gavin]

    Comment by Tom Scharf — 1 Nov 2012 @ 3:21 PM

  15. Apparently, in the last decade or so, surface and lower troposphere temperature has risen more slowly than the long term trend, but ocean heat content to 2km has risen faster than the previous two decades. What could the physical reason be for that?

    [Response: A decadal variation in the rate of deep ocean heat uptake. This uptake is related to advective effects in the North Atlantic and Southern oceans, as well as through diffusion, and we know that the circulations have decadal and multi-decadal variability, thus one can imagine a situation where the advection to depth increases for a short time (due to internal variability, or driven by surface wind anomalies), which would take heat to depth, create a negative SST anomaly (relative to what would have been expected), drawing more heat into the ocean, and slightly cooling the atmosphere (again relatively speaking). If this was true, one would expect the anomalous OHT to have increased faster in downwelling regions. I haven't checked though. - gavin]

    Comment by Icarus62 — 1 Nov 2012 @ 4:15 PM

  16. Thought provoking..

    Why not take some data that is one thousand years old and perform a similar analysis with regards to the escalator trends….

    And if you don’t have good enough resolution, simply add enso-like variability to the underlying trend of the proxy data.

    I’m sure you could work backwards from a detailed core from the indo pacific, compare it to data from the same area and the global as a whole today, and deduced a very crude global mean temperature estimate from one thousands years ago.

    It doesn’t have to be accurate. Or use some hockey stick data, whatever.

    My guess is that (shock horror) you will find a “trend”. Hey, you never know, if you look hard enough you might end up going up the down escalator.

    Comment by Isotopious — 1 Nov 2012 @ 4:48 PM

  17. Jos Hagelaars (#12),
    Put another way, I prefer to ask, “Using the same logic and math that you are using now, you would have been 0 for N in the historical record; what makes you think you are right this time?”

    Comment by Chris G — 1 Nov 2012 @ 5:07 PM

  18. ” One has to consider the opposite condition, if all the simulations were under-estimating temperatures, would there not be rampant speculation that climate sensitivities were too low?”

    It would depend on what ENSO and the sun and volcanoes were doing. If ENSO trends were driving faster warmth, the sun was hot, and volcanoes dormant, then it would not be appropriate to think that simulations running cold was indicative of a high sensitivity. If ENSO, solar, and volcanic activity were as observed currently, and simulations were running cold, I think that high sensitivity would definitely be a useful speculation. (oceanic temperature trends would be an important partner to surface air temperature trends, too)

    Comment by MMM — 1 Nov 2012 @ 5:08 PM

  19. Few nitpicks:
    – improvements are*
    – The magenta decadal trends drawn should date back to ’62 as you include five in the description, yet only four on the graph

    [Response: No. The graph starts in 1975, so only four decades are included. - gavin]

    – tendency of the* planet to warm
    – The UAH data is v5.4, v5.5 limits the recent deviance
    – “no hidden either warming or cooling jumps” reads awkwardly
    – “But despite the fact that August 1997 was shamelessly cherry-picked by David Rose because it gives the lowest warming trend to the present of any point before 2000″ – It was picked to show 15 years, not the lowest trend. If he were to have desired the lowest trend (or better yet a negative one) he could have done so beginning with other dates prior to 2000.

    [Response: Actually no. Aug 1997 gives the lowest trend of any point prior to 2000. - gavin]

    Also, why is trending from August of 1975 itself not considered an arbitrary beginning point?

    [Response: You can show that there is significant break in the trend around 1975, but feel free to do your own analysis starting whereever you want. The whole point of the post is that one should not draw conclusions about the future from short term trends. - gavin]

    Upon glancing over all the data of HadCRUT4 it seems a rather cold spot to start from, although perhaps you were simply trying to start a trend line from around the 0.0 point (albeit a bit under)? However, this is quite arbitrary as well because 0.0 points are also assigned based upon subjective time-frame selections. If, for example, we were to create a piece-wise continuous trend keeping your own trend, we’d find the 0.17 C decadal warming trend from your starting point preceded by an estimated warming of equal magnitude in the combined 125 prior years (beginning at a time where only 1/4 of the present day coverage existed, thus placing the entire 125 year warming more or less within the margin of statistical insignificance). From there we’d have to enter that abhorrent mess that is proxy data, which one could use to pick out a plethora of enormous warming trends if pulling from the LIA, or again less so (possibly no trend, possibly negative) if starting from the MWP, etc. but I’d rather not even…

    [Response:I have no idea what point you are making here. There are statistical tests that one can use to determine whether a break in the trend is significant so it doesn't have to be arbitrary. - gavin]

    Furthermore, the whole “If we assume for a moment that the ENSO variability and volcanoes are independent of any change in greenhouse gases or solar variability” doesn’t sit very well with me on multiple levels, thus using it to set up an argument seems spurious.

    [Response: If you want to claim that ENSO has been noticeably affected by climate change, I'd like to see the evidence. The complexity of the ENSO timeseries, with uncertain amounts of multi-decadal power and poor model simulations makes detection of a change very difficult. If you can't show an influence, the best thing is to assume independence - at least as a working hypothesis. - gavin]

    This is my first post (hopefully of many, if you’ll tolerate me) on RealClimate and in case you hadn’t noticed (you have) I’m not exactly super confident in current modelling projections or ability to accurately account for past variability. That being said, yes, much of the nonsense you’ll find on WUWT and in the Daily Mail article in question is just that, nonsense.

    Thanks for taking the time to run this site.

    Comment by Jefe — 1 Nov 2012 @ 6:46 PM

  20. What do we know about complex systems?
    Well, ask those who’ve built them:

    BEGIN QUOTE
    ________
    “His biggest contribution is to stress the ‘systems’ nature of the security and reliability problems,”….”That is, trouble occurs not because of one failure, but because of the way many different pieces interact.”

    … “complex systems break in complex ways” — … complexity … has made it virtually impossible to identify the flaws and vulnerabilities …..
    _________
    END QUOTE
    http://www.brisbanetimes.com.au/technology/technology-news/killing-the-computer-to-save-it-20121031-28jze.html

    Comment by Hank Roberts — 1 Nov 2012 @ 7:29 PM

  21. “There are two main responses to complexity in science. One is to give up studying that subject and retreat to simpler systems that are more tractable (the ‘imagine a spherical cow’ approach), and the second is to try and peel away the layers of complexity slowly to see if, nonetheless, robust conclusions can be drawn. Both techniques have their advantages, and often it is the synthesis of the two approaches that in the end provides the most enlightenment. ”

    Beautiful. I am stealing this to use the next time that I get the “science is reductionist and therefore flawed/unreliable/useless” response to some evidence-based point I am making.

    Comment by Ian Musgrave — 1 Nov 2012 @ 9:01 PM

  22. Thank you. Prof. Neumann, who has “built them,” is an advocate (as per the linked article) of learning lessons about them from biology–systems yet-more-complex.

    The level of complexity of climate systems is right up there. This post bears out the advice that if you want to talk to a real sceptic, skip the imposters and talk to a practicing climate scientist.

    Comment by patrick — 1 Nov 2012 @ 9:54 PM

  23. How much would observations have to deviate from the models (and over what time period) to justify questioning their validity? Could some aspect of our situation, e.g. the extreme rapidity of the forcing change, be sufficiently novel to make Earth’s climate respond differently than it has in the past, and could this cause divergence from models based on paleoclimate sensitivity estimates? And finally, what’s the connection if any to Hansen et al.’s “Earth’s energy imbalance and implications”? They argue that climate models respond too slowly, but doesn’t that increase the burden of explanation?

    Comment by Chris Korda — 1 Nov 2012 @ 10:26 PM

  24. Aaron Lewis @ 7 – That’s not how the oceans are warmed by greenhouse gases. See this Real Climate post for explanation.

    Comment by Rob Painting — 2 Nov 2012 @ 2:43 AM

  25. Once more a piece of contrariness – in fact devoted to several points.
    First, I always wander with the obsession with linear trends. Especially when the system is as complex as the global climate. Piece-wise joined or step-like constructs of linear trends (figs 1 and 3) would always suffer from the arbitrariness of the breakpoints. But why assume that the trend is linear? Simple fit to the 1975-2012 HADCRUT monthly data with quadratic and cubic polynomials gives significantly better R^2 over the whole range. And shows decrease in the warming ratio. Very significant decrease in the case of the cubic fit. Now, one may ask: why cubic? why quadratic? To which I reply: why linear? Because GHG increase roughly linearly (supra-linearly)?

    [Response: Linear is pretty close to what one would expect given the the anthropogenic drivers for the underlying forced response, so it isn't such a stretch. There is no expectation that the climate will follow a cubic trend - and the results once the impact of ENSO and volcanoes are taken into account support that. - gavin]

    The data is noisy and tied with many unknowns, so only time will tell…

    [Response: So throw out physics because the future is uncertain? - gavin]

    The second point is with the simulations. To quote: “We saw above that the ENSO-corrected underlying trends are very consistent with the models’ underlying trends and we can also see that the actual temperatures are still within the model envelope”. Well, being within the envelope – if the envelope is as large as it seems, is no bragging point.

    [Response: Agreed. It is not a particularly powerful test. But that is because even simulations from the same model but different initial conditions show a large divergence in short term trends - which underscores the main point above that short term trends are not predictive of long term changes. - gavin]

    The question is: what would be the predicted value of today’s temperature anomaly that the model authors would give without knowing the 2000-2012 measurements? By visual inspection of the density of simulations I think that one would expect something like 0.5C. Significantly away from the measurements.

    [Response: Whether it is significant or not depends on the uncertainties (which you neglect to mention). In fact the 2012 annual values (with the same baseline as in the figure) are 0.49 +/- 0.35 (95% spread), so the current values of the 2012-to-date anomaly (0.24-0.26) are not actually significantly different. - gavin]

    As for the Foster/Rahmstorf paper: adjustment of data to remove specific effects in a NONLINEAR, coupled system is always risky. Climatic cause and effect may be independent in the case of volcanoes, but for MEI such decoupling needs long term studies. As the saying goes: if you massage the data enough, you can get anything.

    [Response: Don't be silly. We know that ENSO has an influence on global mean temperatures and is the largest interannual signal in the surface temperature field. It is completely natural to examine what happens when that is corrected for - particularly since that is the main reason in models why the trends are not linear. Complaining about the procedure because it does actually clarify what the underlying trends look like is post-hoc justification. And no, it doesn't give you 'anything'. - gavin]

    Lastly, with respects to the statements that we know the physics “pretty well”. A recent paper by Graeme L. Stephens, Juilin Li, Martin Wild, Carol Anne Clayson, Norman Loeb, Seiji Kato, Tristan L’Ecuyer, Paul W. Stackhouse Jr, Matthew Lebsock & Timothy Andrews An update on Earth’s energy balance in light of the latest global observations, Nature Geoscience, 5, 691–696 (2012), which indicates significant adjustments to the energy balance MEASURED data shows how far we are from certainty.

    [Response: Again the use of 'significance' without understanding what is being done. The Stephens et al paper is a very incremental change from previous estimates of the global energy balances - chiefly an improvement in latent heat fluxes because of undercounts in the satellite precipitation products and an increase in downward longwave radiation. Neither are large changes in the bigger scheme of things, though you will no doubt be happy to hear the shifts bring the data closer to the model estimates. But really, are you really going to try and pull the 'there is uncertainty, therefore we know nothing' line? That isn't going to fly. - gavin]

    You may think me a “denier” or “sceptic” – but my motivation is different: being a physicist from material science field I am reasonably far removed from political pressures and conflicts. And mu goal is simple: to ask for a focus on data and analyses with an open mind. DO NOT FOLLOW COVEY’S RULE OF “BEGIN WITH THE END IN MIND”.

    [Response: Advice I would proffer to you in return. - gavin]

    Comment by PAber — 2 Nov 2012 @ 5:48 AM

  26. [ Response:… The complexity of the ENSO time series, with uncertain amounts of multi-decadal power and poor model simulations makes detection of a change very difficult. If you can't show an influence, the best thing is to assume independence - at least as a working hypothesis. - gavin]
    Geological records of the Equatorial Pacific would suggest that the frequency and possibly the amplitude of the ENSO oscillations are indeed independent of the climate change.
    http://www.vukcevic.talktalk.net/ENSO.htm

    Comment by vukcevic — 2 Nov 2012 @ 8:02 AM

  27. T Marvell “With a few exceptions, climate scientists ignore this [statistical] expertise and analyze trends in a simplistic manner.”

    The criticism would be better directed at the press and those making claims of “no warming since [insert cherry picked start date here]“. The usual error is to assume that a lack of a statistically significant warming trend implies that there has been a pause in global warming. However that is a statistical non-sequitur, based on a poor understanding of frequentist hypothesis testing, unless the test can be shown to have adequate statistical power (which seems never to be mentioned by those claiming a pause in warming). It is clear from the Telegraph article that Phil Jones understands this point perfectly well, but that David Rose clearly doesn’t.

    Comment by Dikran Marsupial — 2 Nov 2012 @ 9:07 AM

  28. PAber,
    I am surprised that you do not understand the purpose and significance of linear trends, particularly when you emphasize the noisiness of the data. It is simply that in a noisy system, the linear term will likely be the first to emerge from the noise. Higher terms will emerge as we gain more information.

    And again, your criticism of Foster and Rahmstorf seems bizarre. If you have a system with lots of noise, cancelling known components of that noise is a well tested method for bringing out signal. If nonlinearities are important, as you suggest, one would expect the result to be…well, crap, not the emergence of a linear trend, and certainly not a linear trend with magnitude equal throughout the observation period.

    And if you are not desperate, then why are you grasping at straws that will not support you–e.g. the Stephens et al. paper?

    Comment by Ray Ladbury — 2 Nov 2012 @ 9:48 AM

  29. re inline comment on 24,
    What I noted was that the ocean skin equilibrium referenced in RC 5 Sept 06 could be influenced by variations in ocean currents and the cryosphere to affect atmospheric temperature on the scale of decades.

    When warm air blows across cold water, the air cools and the water warms. Even in a time of global warming, an increase in ice sheet melting or deep water upwelling can cool the atmosphere relative to the long term trend. The heat of the system continues to increase at the rate of global warming, however, the partitioning of the heat into the various phases of the system changes. It takes a long time for the various phases of the system to come into equilibrium. And, as long as the system is being forced, the system is by definition, not in equilibrium. It the system is not in equilibrium, then air temperature may not be a good measure of heat in the system.

    Re 25 I have to concur climate change deals with processes related to the melting/decomposition of ice /clathrates. Vapor processes are a important in the system. All of these curves are discontinuous in the region of these materials’ melting points. The curves are kinked. I would say that the failure of the climate models failure to predict Arctic Sea Ice behaviour are partially due to this issue.

    Take a unit of air at temperature of -10 (100% RH) and a unit of air at 10 (100% RH) and mix them together. You do not get 2 units of air at 0 degrees.

    And yet, when you do trends of global data you are averaging air temperatures over intervals where the heat content is not continuous, and thus the trend that is the average temperature does not show the actual trend of the heat content.

    While anomalies are the darling of staticians, where the base line environmental temperatures cross the freezing point/melt point of water, the anomalies from those temperature data sets are just the average of nonsense.

    The solution is to work with the standard deviation of the system’s Gibbs Energy on a period after period basis. That will tell you if the system is gaining or losing energy in a meaningful way and avoids all arguments.

    Comment by Aaron Lewis — 2 Nov 2012 @ 1:48 PM

  30. “No. The graph starts in 1975, so only four decades are included.”

    – Correct, which is why I find the fifth added in the description to be unnecessary.

    “Actually no. Aug 1997 gives the lowest trend of any point prior to 2000.”

    – Is not the August ’97 HadCRUT4 temp anomaly 0.436? If so that would mean there are 14 months (by my count) he could have used between that date and 2000 which would have given lesser or negative trends. February of 1998, for one. That’d then go from 0.745–>0.524 (September 2012 anomaly), so he could claim a negative slope, as many idiots actually have bothered to do by selecting from the Niño peak. Perhaps I’m looking at the wrong data set, if so my mistake, but I thought he chose that date just to go from month to month over 15 years because the Mail’s audience could better “connect” with it in that format, or something along those lines. No doubt he intended to mislead, though that wasn’t a point I was contending.

    [Response: Trend is the ordinary least squares fit to the data - not just the anomaly this month minus the anomaly in 1997. And the trend from august 1997 is 0.033ºC/dec, which is the lowest you can get from any point prior to 2000. From Feb 1998, it is 0.042ºC/dec (95% conf is about +/-0.04ºC/dec). There is no doubt that he picked that start date for that reason. - gavin]

    “You can show that there is significant break in the trend around 1975, but feel free to do your own analysis starting whereever (sic) you want. The whole point of the post is that one should not draw conclusions about the future from short term trends.”

    – I’m not quite sure why you think I’m debating the validity (or lack thereof) of short term linear trends, as I’m clearly not. As per your choosing of August 1975 “There are no reasons either statistically or physically to think that the climate system response to greenhouse gases actually changed in August 1975.” We were at, about, 330 ppm then, correct? If you are suggesting natural variability was chiefly responsible prior to 1975, that would ignore an 18% rise from the baseline 280 ppm. Considering 395 ppm now, shouldn’t the earlier 50 ppm increase have affected temperature almost as much as the later 65 ppm additional increase due to the logarithmic nature of impact?

    [Response: This is the fallacy of the single determinant of climate. CO2 is not the only thing that matters! There are however statistical reasons why 1975 is a break point - breaking the trend there provides a substantially better fit over the whole record (not true for Aug 1997), and if you look at when anthropogenic effects came out of the 'noise' of global temperatures, it is about the same time (fig 9.5 WG1 AR4). But if you want to look at longer datasets, go ahead. -gavin]

    “I have no idea what point you are making here. There are statistical tests that one can use to determine whether a break in the trend is significant so it doesn’t have to be arbitrary.”

    – Basically if you piece-wise your own starting point with the entire HadCRUT4 data set you are left with nothing more than perhaps a couple of tenths, still within the range of noise, for the remaining 125 years, thus making it seem as if you believe GHG forcing only mattered after August of 1975.

    [Response: Not sure how any of that follows. GHG forcing has been important since about 1800, but only substantially larger than everything else since the mid-1970s. If you put in a break point in the whole series (from 1850) in Aug 1975, you get a trend of 0.03ºC/dec before, and 0.16ºC/dec after. - gavin]

    “If you want to claim that ENSO has been noticeably affected by climate change, I’d like to see the evidence. The complexity of the ENSO timeseries, with uncertain amounts of multi-decadal power and poor model simulations makes detection of a change very difficult. If you can’t show an influence, the best thing is to assume independence – at least as a working hypothesis.”

    – But I don’t want to claim that, I want to state the fact that it is impossible to determine at this point in time. Such a tenuous working hypothesis needn’t even be brought into the discussion.

    [Response: Then why are you objecting to a explicit removal of ENSO effects in the time series? - gavin]

    Comment by Jefe — 2 Nov 2012 @ 3:07 PM

  31. Icarus,
    If you just compare the recent data to the long term trend, then yes, it is rising more slowly. However, if you compare the data from the two decades prior, then it is rising much faster than the long term trend. The question is whether this is just noise in the long term trend, or meaningful variations that require more research.

    Comment by Dan H. — 2 Nov 2012 @ 4:57 PM

  32. For all those who thought the Skeptical Science “Up the Down Escalator” post was satire:

    http://www.skepticalscience.com/going-down-the-up-escalator-part-1.html

    I give you Jefe:

    “Basically if you piece-wise your own starting point with the entire HadCRUT4 data set you are left with nothing more than perhaps a couple of tenths, still within the range of noise, for the remaining 125 years, thus making it seem as if you believe GHG forcing only mattered after August of 1975.”

    Jefe apparently does not realize that clean air legislation and the development of catalytic converters (which require low-sulfur fuel) diminished the effects of aerosols around 1975 and in subsequent years.

    Jefe is proof that Poe’s law applies to climate science.

    Comment by Ray Ladbury — 2 Nov 2012 @ 5:38 PM

  33. Using the Core BJ8-03-31MCA, Makassar Strait, Indonesia (Oppo et al. 2009 Nature 460:1113),

    There is a 30% relationship between gistemp (3 year res.) and Indo -pacific temps with a 40 -50 year lag. The series is only 42 data points long (equating to 126 years), so is hardly robust, however, it may be a useful predictor of future temps since it is gistemp that lags the SST.

    The correlation is centered on the rapid warming which occurred between 1980 – 1998 in gistemp and the rapid warming which (apparently) occurred between 1936 -1960 in Indo SST.

    The significant lag time and short length could mean the relationship is simply due to chance, if however the relationship holds true, it would be a remarkable superposition and extremely unlikely due to humans.

    http://www.ncdc.noaa.gov/paleo/recons.html

    Thus is the danger of interpreting short trends…anyone can do it…

    Comment by Isotopious — 2 Nov 2012 @ 5:49 PM

  34. Seasonal-to-Decadal Predictions of Arctic Sea Ice: Challenges and Strategies (pre-publication)

    by
    Committee on the Future of Arctic Sea Ice Research in Support of Seasonal-to-Decadal Predictions; Polar Research Board; Division on Earth and Life Studies; National Research Council
    available at
    National Academies Press online
    (On topic because a theme is lack of observation data.)

    Comment by Aaron Lewis — 2 Nov 2012 @ 5:59 PM

  35. Just to add as an after thought, you could also add 6 month lag El Nino data to the Indo proxy, which could increase the correlation with gistemp, given that it would be a far cry to expect anything higher from something that occurred half a century ago, but there it is.

    Comment by Isotopious — 2 Nov 2012 @ 6:11 PM

  36. Aaron Lewis @ 24 – “What I noted was that the ocean skin equilibrium referenced in RC 5 Sept 06 could be influenced by variations in ocean currents and the cryosphere to affect atmospheric temperature on the scale of decades”

    This is what you wrote @ 7:

    I assert that recently, more of the heat in the atmosphere has gone into warming the oceans and warming/melting ice. Thus, today, we have warmer ice, warmer oceans, and relatively cooler air.

    That is wrong. That’s not how the physical world operates, in climate models perhaps, but not Earth. The transport of energy into the ocean is via shortwave radiation (sunlight), whereas the longwave radiation (heat) forcing, from the atmosphere, governs how much energy is retained in the ocean. That is the fundamental background that you have misinterpreted.

    Even if longwave fluxes into the ocean proper were physically possible, the huge disparity in heat capacity between the ocean and atmosphere would barely register in ocean heat content uptake. I think you need to read the post by Professor Minnett again, and perhaps look at the 2011 paper by John Church & colleagues.

    There’s a very simple reason why global surface temperatures have been cool of late – the La Nina-dominant trend of the last 6 years has buried more heat in the subsurface ocean, and the sea-air flux of heat exerts a large influence on global surface temperature. This will not last. Even an apparent global dimming trend in the last decade has been unable to slow the inexorable warming of the global oceans.

    Comment by Rob Painting — 2 Nov 2012 @ 9:33 PM

  37. That’s not how the physical world operates, in climate models perhaps, but not Earth.

    Want to back up this smear against physics-based models with some hard evidence?

    Comment by dhogaza — 3 Nov 2012 @ 1:42 PM

  38. Re 36
    My point is not about how the ocean warms/cools as a result of radiation/GHG, but the more neglected area of the stability of the heat partition between the phases.
    I think the heat partition between phases is much less stable than has been assumed, and the implications for AGW have not been thought though. In particular, the implications for the detection and monitoring of AGW as the system warms have not been fully considered.
    I do not think atmospheric temperatures are a consistent and precise proxy for the total heat content of the global system. Tiny changes in heat transfer between the atmosphere and the oceans affect the temperature of the atmosphere. One real world example of this was offered in the last paragraph of comment 36.
    La Nina/ PDO is a perfect example where changes in ocean currents/ocean upwelling affect heat transfer between the phases of the system (and cool the air) – on a human time scale. In La Nino, global air temperatures cool, and that heat goes where? Well, some of it goes into the ocean.
    In the real world, sometimes air does heat water, and sometimes water does transfer heat to air. Air-water heat flux may not significantly affect the temperature of the ocean, but it does affect the temperature of the atmosphere – as in the air over Europe is warmed by the North Atlantic Drift.
    Water- air heat flux also affects the latent heat content of the atmosphere as moist air contains more heat than dry air of the same temperature. Thus, we cannot do arithmetic on air temperatures and assume that the result reflects the total heat in the air. That kind of stuff is ok as an educational exercise, but if we are going to do engineering and public policy planning we need to either insert safety factors or work with the Gibbs energy. If we are going to work with Gibbs energy, we need to be careful to bound and define the systems, and to ensure that we understand the nature of the equations of state, e.g., kinked curves.
    One simply cannot do arithmetic (least squares trends) on the temperature of environmental air and expect the result to reflect the changes in heat content. As AGW moves forward, the latent heat content of the air changes, so that air of the same temperature has more heat in it, and warmer air has even more heat in it. HadCRUT4 does not reflect the latent heat in the atmosphere! Thus, plots of HadCRUT4 data do not reflect the full amount of atmospheric warming.
    Recently documented changes in atmospheric circulation patterns mean that ocean currents are changing. If La Nina/El Nino can affect global air temperatures in a period of a few years, than other changes in ocean currents (driven by AGW) can affect global atmospheric heat content in a few years.
    We can no longer assume that it takes generations and generations for a change in ocean currents to have a real impact on humans. We have that lesson in El Nino.
    My comment on Church (2011) is that they do not account for heat that has gone into warming ice, which does not get warm enough to melt. In a time of moulin formation on the GIS, this is a non-trivial.

    Comment by Aaron Lewis — 3 Nov 2012 @ 2:37 PM

  39. ” “That’s not how the physical world operates, in climate models perhaps, but not Earth.”
    Want to back up this smear against physics-based models with some hard evidence?”

    sigh… the old “cold can’t transmit” whine. Totally ridiculous. Convert from English to Science-speak instead of trashing English, and avoid pointless arguments about nothing.

    Comment by Jim Larsen — 3 Nov 2012 @ 3:56 PM

  40. I sure would be very grateful if someone could shed some light on the questions I asked @23. Gavin? Jim? Anyone? Or if they’re poorly formulated please tell me so I can improve them. I’m not being contrary or anything like that, I’m just trying to understand.

    [Response:On your 2nd question, I don't know about the speed of the radiative forcing creating novel situations, but there is good reason to be concerned that the speed of the temperature increase itself could indeed cause states that modern society has not encountered. That's a slightly different issue of course--Jim]

    Comment by Chris Korda — 3 Nov 2012 @ 4:49 PM

  41. What does the hindcast of the models and temperature look like from 1880-2012?

    Comment by Camburn — 3 Nov 2012 @ 6:29 PM

  42. Rob Painting @ 36:
    Global dimming has changed trends. The earth is now presently approx 4% brighter than in 1990.

    Recent reversal

    In 2005 Wild et al. and Pinker et al. found that the “dimming” trend had reversed since about 1990 [8]. It is likely that at least some of this change, particularly over Europe, is due to decreases in pollution; most governments have done more to reduce aerosols released into the atmosphere that help global dimming instead of reducing CO2 emissions.

    The Baseline Surface Radiation Network (BSRN) has been collecting surface measurements. BSRN didn’t get started until the early 1990s and updated the archives. Analysis of recent data reveals the planet’s surface has brightened by about 4 % the past decade. The brightening trend is corroborated by other data, including satellite analyses

    Comment by Camburn — 3 Nov 2012 @ 6:39 PM

  43. It seems to me (a rank amateur) that the most reasonable way to estimate temperature trends due to CO2 increase is to find the statistical correlation between the CO2 and the temperature anomaly time series. Using NASA’s CO2 series for 1850 -2011 (http://data.giss.nasa.gov/modelforce/ghgases/Fig1A.ext.txt) and NASA’s temperature anomaly series http://data.giss.nasa.gov/gistemp/graphs_v3/Fig.A2.txt) I find that for the period 1880-2011 the two series correlate with R-sq~.86. Using the natural log of the CO2 may be more appropriate, but it makes little difference for the specified time period since the CO2 level increases by “only” 35%. The logarithmic relationship is Anom =0.17+3.12ln(CO2/341) deg K, where CO2 is the annual level ppm, and 341ppm is the average of the beginning and end point levels. NASA gives a “2 deg K” CO2 scenario for the time period 2012- 2099. It ends with a CO2 level of 560 ppm. With this scenario the above statistical model projects the expected 2. deg K for the 1880-2099 temperature change (a simple linear model would give 2.5 deg K).

    The “random” fluctuations about this trend due to El Nino’s etc have a standard deviation of 0.1 deg K. Only two data points deviate from the model predictions by more than 2 standard deviations. For the years 2001-2011 inclusive, the actual anomaly was above the model prediction 8 times, below 3 times. All the data points for this period are within 2 standard deviations of the statistical model.

    Short term trend estimates seem to be an exercise in futility. For example, based on the temperature data, the average 10 year trend (using moving 10 year intervals) is 0.07 deg K/decade. The standard deviation of the trend is double this, 0 .14 deg K/decade. Roughly speaking, the frequency spectrum of the noise (El Nino etc) has components at higher frequencies than those of the signal (CO2), so differentiation (finding the trend) worsens the signal to noise ratio.

    Based on this, I suggest that the best way to monitor trends would be to use a statistical correlation model (such as the above)and check if new data points fall within 2 standard deviations of the model predictions.

    Comment by Dave Griffiths — 3 Nov 2012 @ 7:33 PM

  44. Jim Larsen @ 39 – It’s evident you don’t comprehend the post by Professor Minnett. Try reading it again, and see if it is any clearer to you. I think he’s done a sterling job of explaining the fundamentals of an incredibly complex, and counter-intuitive, issue.

    If you can’t parse that, I doubt you are going to follow the primary peer-reviewed literature itself. And your comment about “cold can’t transmit” demonstrates you have no understanding of the topic under discussion. Until you do, further discussion will prove fruitless.

    Comment by Rob Painting — 3 Nov 2012 @ 8:44 PM

  45. Camburn @ 41 – Skeptical Science seems to be down at the moment, but I’ve written a recent post on Hatzianastassiou (2011). It is the 2nd such peer-reviewed study to find a dimming trend in the noughties. Note that the surface station networks show a good agreement (in a statistical sense) with the modelled tendencies from the satellite-derived data.

    Time will tell how well this holds up, but there are other global datasets that might give some insight.

    Comment by Rob Painting — 3 Nov 2012 @ 9:02 PM

  46. Dhogaza @ 37 – That seems to be a kneejerk reaction. “Slur” is highly emotive. Perhaps you can explain to me how a micro-physical effect, such as the reduced thermal gradient in the cool skin layer, is simulated in the ocean models?

    And just for the record; unless one want to resort to goat entrails, and reading tea leaves – as contrarians might have us do, there is no alternative but to use climate models. But wouldn’t it be great if the model spread was greatly reduced, and they exhibited greater accuracy?

    Comment by Rob Painting — 3 Nov 2012 @ 9:12 PM

  47. Mr. Aaron Lewis writes on the 3rd of November, 2012 at 2:37 PM:
    “…work with the Gibbs energy…”

    while i agree about the partitioning of heat flux into phase change, which particular gibbs free energy are you referring to ? both phase change of ice to water and water to vapour are involved. and more.

    melting ice seems to be around 1e21J, so far. erosion of cold content as Prof. Jason Box puts it is …?

    sidd

    Comment by sidd — 4 Nov 2012 @ 12:10 AM

  48. PAber (25) suggests that a linear model of temperature growth might not be appropriate. In support of that I note that CO2 appears to be growing expodentially. Also physics models of AGW contain feedbacks, which suggest non-linear growth.

    [Response:But the radiative forcing is the natural logarithm of the [CO2] ratio at two time points.–Jim]

    He also says that one must watch out for research that starts at the end, or what I call “result-oriented research”. Both AGW advocates and skeptics accuse each other of this. In practice it’s hard to tell whether one is quilty, so it makes charges easy. I can suggest several tests: whether the researcher uses SOP, whether the researcher uses the best data, whether there is thorough robustness analysis (concerning methods and data alternatives), whether the discussion seems balanced, whether the data and programs are made available to other researchers, and whether the researcher is associated with an advocacy organization.
    If one spots odd procedures in a paper, one can ask the author to explain them. If the author doesn’t, the paper can be dismissed.
    I disagree with the suggestion that short-term climate trends have little meaning, but their usefulness occurs only in relation to longer trends. They are important when testing time series models. Researchers routinely model long time series based on theories of what affects the variable in question A good way to test the model is to see whether events in future periods conform with what the original model pedicted. It’s a difficult procedure, but commonly done. Of course, the subjects of this post wouldn’t think of doing that. Their failure do so is a good argument against them – e.g. “what model of AGW climate change are you using when you say that recent trends do not support AGW?”

    Comment by T. Marvell — 4 Nov 2012 @ 12:38 AM

  49. > cool skin layer is simulated ….

    LMGSTFY or this blog post may help

    Comment by Hank Roberts — 4 Nov 2012 @ 12:52 AM

  50. In his inline responses to my quick post (#25) gavin set out several remarks that actually more than anything else validate my points. Let me answer in return.

    // on using linear trends //

    [Response: Linear is pretty close to what one would expect given the the anthropogenic drivers for the underlying forced response, so it isn't such a stretch. There is no expectation that the climate will follow a cubic trend - and the results once the impact of ENSO and volcanoes are taken into account support that. - gavin]

    To limit ourselves to phenomena with a fixed rate of change would be fine – if we would not observe significant changes in these rates, bot in the long time view (where climate changes are definitely NOT linear) or even in the short time range (where one could use the linear/ first derivative approximations). But at the very moment when one considers joined piecewise linear approximations [fig 4], without giving the reasons why the system would change its characteristics at that very time, perhaps it is more sensible to look for mechanisms (or effects, if we are unsure of the mechanisms) that describe the changing rate of change (leading to quadratic description) or perhaps even other functional forms: periodic, logistic, cubic. Sure the antrhopogenic GHG do increase linearly, but the system they are “inserted” into is not linear – this is my core point. Linearizing nonlinear system is computationally risky. More on this in later comment.

    I wrote”
    “The data is noisy and tied with many unknowns, so only time will tell…”
    [Response: So throw out physics because the future is uncertain? - gavin]
    No, definitely. I do not advocate throwing out physics. But with the very sparse data that we have available and with the complexity of the system: are we sure we know all the physics to put in?
    Let me answer by a simpler example. Suppose one is to describe the behavior of a transistor (let alone a coupled system of transistors such as an integrated circuit), using Ohm and Kirchoff laws. The switching, nonlinear behavior of the transistor might be very difficult to explain using these linear laws, without the knowledge of the internal structure of the transistor. Moreover, perhaps one would lack the idea to measure the gate voltage, in which case the results would be truly bizarre: the same source/drain characteristics would produce different results in separate measurements. Would throwing doubt on such measurements and attempts to “linearize” the transistor amount to throwing out the Ohm and Kirchoff laws?
    Now, to validate the analogy: the climate system is a system of interacting components. Worse, the basic hydrodynamical equations are themselves nonlinear, which makes the description of their interactions and influences even more difficult. I do not advise throwing out radiation physics, N-S equations, absorption/emission curves and any of the physics already involved. I question if we, indeed, use all the necessary knowledge and if we are not missing key couplings between the systems.

    On simulations accuracy
    [Response: Agreed. It is not a particularly powerful test. But that is because even simulations from the same model but different initial conditions show a large divergence in short term trends - which underscores the main point above that short term trends are not predictive of long term changes. - gavin]
    [Response: Whether it is significant or not depends on the uncertainties (which you neglect to mention). In fact the 2012 annual values (with the same baseline as in the figure) are 0.49 +/- 0.35 (95% spread), so the current values of the 2012-to-date anomaly (0.24-0.26) are not actually significantly different. - gavin]
    What worries me – to the point of actually rising the issue – is not only the spread of the results – but the fact that they depend so much on the models and the starting data. The spread for the hindcast phase is almost as significant as for the forecasting phase. To me this is as close to a proof as I may have that the points I made above, about our lack of a good model, are valid. If I tried to come out with similar “theoretical model” in solid state physics, my papers would be summarily rejected. Yet, in climate science we keep them – because we (at least for the moment) do not have anything better. Gavin: are you truly satisfied with the quality of the model results (especially hindcast)?

    [Response: Don't be silly. We know that ENSO has an influence on global mean temperatures and is the largest interannual signal in the surface temperature field. It is completely natural to examine what happens when that is corrected for - particularly since that is the main reason in models why the trends are not linear. Complaining about the procedure because it does actually clarify what the underlying trends look like is post-hoc justification. And no, it doesn't give you 'anything'. - gavin]
    Why should I be silly to assume that not only ENSO drives the climate changes on a global scale (I do) but also that ENSO depends on these changes (probably to an unknown degree)? This is what I meant by dividing the volcanic/sun/possible meteor impact and other “climate independent” events. I complain to the process of decoupling ENSO because it separates this signal without proving that it is indeed separable on a cause/effect level.

    On the global energy flux issue.
    [Response: Again the use of 'significance' without understanding what is being done. The Stephens et al paper is a very incremental change from previous estimates of the global energy balances - chiefly an improvement in latent heat fluxes because of undercounts in the satellite precipitation products and an increase in downward longwave radiation. Neither are large changes in the bigger scheme of things, though you will no doubt be happy to hear the shifts bring the data closer to the model estimates. But really, are you really going to try and pull the 'there is uncertainty, therefore we know nothing' line? That isn't going to fly. - gavin]
    Yes and no: Yes I am claiming that we do not know the system well enough. No, I do not claim we know nothing.
    Let me answer firs with respect to the new flux balance. Some of the changes – es they are corrections – touch the “small” but important areas, such as cloud effects. Important because – to my knowledge – a lot of model uncertainty is tied with them. So, I agree with Gavin’s optimism: if new models/or even old models with the new data would reproduce observations better – I would be more willing to trust them.

    But my whole point is: I think we are still too far away from a model that would allow quantifiable predictions. Thus the focus should be on: gathering the data – more varied, better quality, better resolution. In parallel, on developing the models with an open mind. Not to search for proof of AGHG influence or to scare the public, but to understand what is happening. I track the political efforts on both sides, the “majority” and the “sceptics” (or if one prefers another type of language, the “alarmists” and the “deniers”) and I see that too much of the discussion has changed into nonscientific grounds. Too many scientists have become politicians, ready to support their camp anyway they can.

    And that is a true problem for me.

    Comment by PAber — 4 Nov 2012 @ 1:18 AM

  51. Aaron Lewis @ 38 – “In La Nino, global air temperatures cool, and that heat goes where? Well, some of it goes into the ocean. In the real world, sometimes air does heat water, and sometimes water does transfer heat to air.”

    It’s almost as if you’re immune to learning. This is what Professor Minnett wrote in the Real Climate post I directed you to:

    “…..how can a forcing driven by longwave absorption and emission impact the ocean below since the infrared radiation does not penetrate more than a few micrometers into the ocean? Resolution of this conundrum is to be found in the recognition that the skin layer temperature gradient not only exists as a result of the ocean-atmosphere temperature difference, but also helps to control the ocean-atmosphere heat flux.

    The ‘skin layer‘ is the very thin – up to 1 mm – layer at the top of ocean that is in direct contact with the atmosphere). Reducing the size of the temperature gradient through the skin layer reduces the flux. Thus, if the absorption of the infrared emission from atmospheric greenhouse gases reduces the gradient through the skin layer, the flow of heat from the ocean beneath will be reduced, leaving more of the heat introduced into the bulk of the upper oceanic layer by the absorption of sunlight to remain there to increase water temperature”

    You are, of course, entitled to believe whatever you wish, but isn’t misinformation best left to the contrarians?

    Comment by Rob Painting — 4 Nov 2012 @ 2:46 AM

  52. Hank Roberts @ 49 – google “parameterization”, as it applies to climate modelling. It is not the same as simulating an actual physical process.

    Comment by Rob Painting — 4 Nov 2012 @ 2:09 PM

  53. Re- Comment by PAber — 4 Nov 2012 @ 1:18 AM:

    You say- ” In parallel, on developing the models with an open mind. Not to search for proof of AGHG influence or to scare the public, but to understand what is happening. I track the political efforts on both sides, the “majority” and the “sceptics” (or if one prefers another type of language, the “alarmists” and the “deniers”) and I see that too much of the discussion has changed into nonscientific grounds. Too many scientists have become politicians, ready to support their camp anyway they can.”

    Because this statement was made in the context of doing actual climate science, you are referring to a fairly large group of scientists and suggests to me that you must be aware of a sizable subgroup of practicing climate scientists that elicit this behavior. I am not aware of this trend. I would be interested in hearing of some reliable evidence for this statement. Steve

    Comment by Steve Fish — 4 Nov 2012 @ 2:29 PM

  54. Regarding the issue of non-linearity raised by PAber, Chris Korda, and others:

    These are all interesting points, but no model (of any complexity that I am aware of) shows evidence of behavior that deviates significantly from global temperature being a relatively smooth function of CO2 concentration, at least over the range of conditions we are interested in for the global warming problem.

    In fact, a substantial body of work has shown that global temperatures are a linear function of CO2 emissions, with the total cumulative carbon emissions from humans providing a useful metric in determining the peak amount of global warming. It is also here where one needs to discriminate between long-lived forcings such as CO2, and short-lived forcing agents such as methane or aerosols, which can dominate the short-term behavior of global temperature, but have no discernible impact on the century-to-millennium scale trend.

    It is of course possible that Earth resides rather close to a bifurcation point, analogous to a Snowball Earth scenario, but there’s little indication in the Holocene or Pleistocene record that such a tipping point is readily triggered. These scenarios do play out in simulations over a rather broad range of forcing (Gary Russell’s model at NASA GISS produces such behavior around 8xCO2-16xCO2 due to rapid cloud changes) and one can also look at warm climates of the past (e.g., the Pliocene, with boundary conditions very similar to today, but with a pretty different climate). Identifying where these bifurcations are and the degree to which hysteresis exists in the system is still a big question in climate sensitivity, and one in which some current methodologies of answering the question are inadequate.

    Comment by Chris Colose — 4 Nov 2012 @ 6:55 PM

  55. re 51
    Rob,
    My background is chemical engineering. I rose to be Senior Scientist at one of the world’s largest engineering firms because I asked better questions (And, because I was good at finding mistakes, such as unwarranted assumptions.)

    My areas of expertise were hazardous waste; environmental fate and transport; risk assessment and control; environmental sampling, analysis, and data management; and climate change.

    I find that the use of technical language tends to restrict the paradigms available for analysis of the question. Thus, I try to ask questions in the most general language possible.

    I spent a fair amount of time writing US DOE manuals, and I do tend to get stuff correct. I choose my teachers with great care

    Actually, there are a fair number of rather competent old guys around, and here, today, you have been condescending to at least two of us.

    Comment by Aaron Lewis — 4 Nov 2012 @ 8:02 PM

  56. #54 Chris Colose: I presume you mean a linear function of log(CO_2 concentration).
    As for nonlinearities, these are most likely to happen in easily observable effects like sea ice loss.

    Comment by Philip Machanick — 5 Nov 2012 @ 6:02 AM

  57. Aaron,
    Fear not. There appear to be many with a similar condescending attitude, and some are not even scientists! You previous points are issues that definitely need to be answered, but have not been addressed thoroughly. Some cannot at the moment. The recent La Nina seems to be the catchall for many of the recent observations; cooling, sea level decline, droughts, floods, Sandy, etc.

    I find nothing wrong with posing questions in the most general manner possible. Oftentime, the use of technical language is meant to impress and demean, rather than address the issue at hand. I too feel that the ENSO/atmospheric interaction is much more important in global climate than many other people contend.

    Comment by Dan H. — 5 Nov 2012 @ 7:07 AM

  58. My areas of expertise were hazardous waste; environmental fate and transport; risk assessment and control; environmental sampling, analysis, and data management; and climate change.

    That may be so old timer, but some of us have been around long enough to know that ounce of prevention is worth a metric ton of remediation, and understand that your work is for the most part a result of bad decisions by these so called experts which have resulted in easily preventable environmental catastrophes, many of them large scale and ongoing. When you can address that, let me know.

    Thanks.

    Comment by Thomas Lee Elifritiz — 5 Nov 2012 @ 8:25 AM

  59. [Response: I try a different way. To your point 3 the answer is yes - the ocean surface is on average warmer than the overlying air, because the ocean absorbs a lot of heat from the sun, part of which it passes on to the air above. Your confusion arises simply because we are now discussing how the bulk of the ocean below the skin layer gets heated. Thus we are talking not about the gradient between sea surface and overlying air, but we are talking about the gradient through the skin - i.e., the water temperature difference between the top and bottom of the skin layer, which controls how heat flows across this layer, from the bulk of ocean water below to the surface. Obviously, if you heat the top of the skin layer, this reduces the heat flow across this layer from below. Clear? Or still confusing? -stefan] …

    Just guessing here, but I think the above response in the comments for the RC article by Minnett discusses where Rob Painting thinks Aaron Lewis is misunderstanding the skin layer and how the enhanced GHE slows heat loss from the oceans, which, obviously, results in increased OHC.

    On Rob’s point about La Nina driving ocean heat to deep layers, that makes sense to me, but I haven’t found much to confirm it on Google Scholar. As for its consequences, one scientist says the additional heat in the 700-meter to 2000-meter layer, and deeper, will come out and get us. Another says it’s locked up in Neptune’s brig for years numbered in the thousands.

    El Ninos appear to increase the surface air temperature. La Nina appear to cool it. This seems to be absent of controversy.

    But how they do this is really two very different processes, and they are often described as simply undoing the similar work of the other. I do not see how that can be the case.

    It all could use a very precise RC article: the different ways and timescales by which heat transfers between the atmosphere and the oceans (including what happens to it), and whether anything actually could stall what appears to be a continual warming of the oceans during the alleged “pause” in global warming?

    Comment by JCH — 5 Nov 2012 @ 10:39 AM

  60. Re 58
    I wish! I did a lot of work on the cleanup of the Hanford Washington plutonium production facility in the 1990s. Much of the worst contamination was a result of structures that my boss had designed as a junior engineer 30 years before.

    He was not a bad guy. He built what “management” had told him to build, and management was in a panic over the cold war. By then, they all knew better, but they went ahead and dumped all that radioactive material into the soil.

    The lesson is one that should be taken to heart. Not dumping is always cheaper than trying to cleanup afterward. A little thinking and planning can save a huge amount of money, health issues, and even lives. This includes radioactive materials, toxics, and green house gasses.

    “Management” is always panicked about something. Then, it was the cold war, now it is the “economy.” The least damage to the economy will be caused by the least emissions of GHG. More AGW will require more government intrusion into our lives. Conservatives should be the strongest opponents of fossil fuel emissions.

    Comment by Aaron Lewis — 5 Nov 2012 @ 12:33 PM

  61. Philip,

    I actually didn’t have CO2 concentrations in mind, but the relation between cumulative carbon emissions and peak global temperature (something in the neighborhood of 2 C per 1000 GtC) which has been identified as being nearly linear over a reasonable range (see the NAS 2011 Climate Stabilization Report).

    Because the human influence on climate can be represented by a single statistic, cumulative carbon, it can provide an alternative metric -just like GWP or CO2-equivalent, in thinking about the evolution of global temperatures.

    But concerning the main point, the radiative impact of adding CO2 to the atmosphere in isolation is a solved problem, and it doesn’t feature any rapid behavior changes over a narrow concentration range. Consequently, any ‘threshold’ behavior that exists in the system must arise from the collective interaction of the various feedbacks. Arctic sea ice loss can be an example of a tipping point, but it’s primarily a tipping point for nothing else than itself (i.e., Arctic sea ice loss, and associated ecological systems, etc)– but without much impact on the energy budget of the entire planet or on global climate sensitivity. That doesn’t mean it’s unimportant, but should be kept in perspective for the climate sensitivity issue.

    Comment by Chris Colose — 5 Nov 2012 @ 1:17 PM

  62. > Rob Painting … google “parameterization”,
    > as it applies to climate modelling

    Here ya go:

    What are parameterisations?

    Comment by Hank Roberts — 5 Nov 2012 @ 1:27 PM

  63. > bad decisions by these so called experts which have
    > resulted in easily preventable environmental catastrophes

    Those making decisions may believe they and theirs will be exempt from the consequences if the decisions are wrong.
    This may have to do with discounting the future value of anything, which economists do.

    Comment by Hank Roberts — 5 Nov 2012 @ 2:36 PM

  64. Some of the previous discussion seemed to confuse two types of linearity (a)climate models for which temperature depends linearly on ln(CO2); (b) CO2 time histories for which ln(CO2/CO2ref) increases linearly with time. First note that (b) is far from true. If we take the NASA CO2 data it is clear that the slope of ln(CO2/CO2ref) changes considerably with time. For example, taking some time periods with roughly constant slope, we have (slope x 1000 for easy reading):
    1900 – 34: 1000*slope = 1.23/year (note CO2ref does not affect the slope)
    1935 – 49: 1000*slope= 0.114/year (Depression, WWII etc)
    1950 – 58: 1000*slope= 1.67/year (recovery stage 1)
    1959 – 75: 1000*slope=2.92/year (now things are moving)
    1976 – 94: 1000*slope=4.36/year (more and more growth)
    1995 – 2011: 1000*slope=5.11/year (China kicks in?)
    It is quite evident that the current slope of ln(CO2) is much greater than that for 1900-34.
    On the other hand, if you correlate the temperature anomaly to ln(CO2) (see 43 ), then you find a good linear relationship (Anom =0.17+3.12ln(CO2/341) deg K; rsq~0.86). This statistical model predicts a transient 2 deg K increase for CO2 doubling, in good agreement with the big models. To me this is not surprising since 2 deg K only represents a 0.7% increase in the average global absolute temperature. The big problem is that human civilization is extremely sensitive to small changes in the long-term average temperature.
    The increasing rate of increase of ln(CO2) presumably reflects economic developments. Having just spent a year in China I would not be surprised to see the slope of ln(CO2) increase quite a lot more. I tried fitting the current CO2 data to a logistics function, and that worked extremely well. If the future is like the past then CO2 will reach 560 ppm by 2060. But given the noise in the temperature signal it may be a while before the consequences can no longer be ignored by anyone.

    Comment by Dave Griffiths — 5 Nov 2012 @ 3:53 PM

  65. PAber,
    If I may say so, you have an utterly bizarre idea of how physical models are built. You seem to think that unless the entire model springs full grown from the head of Feynmann that it will be worthless for prediction. This is utter horse crap.

    Climate models have a pretty good track record of successful predictions.

    http://bartonpaullevenson.com/ModelsReliable.html

    That you do not realize this is telling. Might I suggest choosing another orifice out of which to speak.

    Comment by Ray Ladbury — 5 Nov 2012 @ 7:16 PM

  66. To Ray Ladbury, who wrote:
    [PAber,
    If I may say so, you have an utterly bizarre idea of how physical models are built. You seem to think that unless the entire model springs full grown from the head of Feynmann that it will be worthless for prediction. This is utter horse crap.
    Climate models have a pretty good track record of successful predictions.
    http://bartonpaullevenson.com/ModelsReliable.html
    That you do not realize this is telling. Might I suggest choosing another orifice out of which to speak.]

    A point by point reply is in order:
    Working as active physicist for over 30 years I may have some preconceptions as to how one build models and when one judges them to be adequate. No, I do not think they are jump out of someones head “complete and perfect”, except for some very rare, very fortunate cases. Especially for the climate modelling, which attempts to deal with an extremely complex system. So, by all means we should work on improvements, step by step.

    But to judge if the current status of the models is good enough to call their results “predictions” is another matter. My remarks were based on the figure provided by Gavin, which show clearly a huge spread of results (both hind- and forecasted. Extrapolated to 100 years these would diverge even more. Yet, we happily postulate, to the public, simple numbers: 3C by the end of the century, or 5C or whatever the current fancy is. I question the validity of using the model results in such political aims. Because science can be (and will be) improved, as we gather more data, make more accurate guesses as for the feedback mechanisms etc. But the public propaganda can not be “retracted” as easily as a research paper.

    When 1 standard deviation (to quote Gavin) is about 75% of the modelled effect (see Gavin’s reply to my first post) then, in my opinion, the model result is crap (to use your word). Unless you WANT to use it, for nonscientific purposes.

    As for the personal suggestion – this is also very telling. To denigrate someone (anyone?) who disagrees is a clear sign of no other argument. My suggestion – if I may say so – is that your post would look much better without the last remark.

    Comment by PAber — 6 Nov 2012 @ 2:02 AM

  67. PAber,
    First, climate is inherently about trends, so the criterion for a climate model is whether it is getting the trends more or less correct. Climate models do pretty well by such criteria.

    Did you even bother to look at the list I linked to, or did you simply dismiss it out of hand? Because, certainly, the list includes some impressive successes that I think deserve more than a dismissive wave of the hand. I will reproduce it here for your benefit in case you find reading a link too burdensome.

    That the globe would warm, and about how fast, and about how much.
    That the troposphere would warm and the stratosphere would cool.
    That nighttime temperatures would increase more than daytime temperatures.
    That winter temperatures would increase more than summer temperatures.

    Polar amplification (greater temperature increase as you move toward the poles).
    That the Arctic would warm faster than the Antarctic.
    The magnitude (0.3 K) and duration (two years) of the cooling from the Mt. Pinatubo eruption.
    They made a retrodiction for Last Glacial Maximum sea surface temperatures which was inconsistent with the paleo evidence, and better paleo evidence showed the models were right.

    They predicted a trend significantly different and differently signed from UAH satellite temperatures, and then a bug was found in the satellite data.
    The amount of water vapor feedback due to ENSO.
    The response of southern ocean winds to the ozone hole.
    The expansion of the Hadley cells.

    The poleward movement of storm tracks.
    The rising of the tropopause and the effective radiating altitude.
    The clear sky super greenhouse effect from increased water vapor in the tropics.
    The near constancy of relative humidity on global average.
    That coastal upwelling of ocean water would increase.

    You can find links to the research on Barton’s page. Some of these predictions are not trivial at all.

    You also seem to be confused with respect to the degree of expected. There are about a dozen independent lines of evidence, all of which favor warming of around 3 degrees per doubling of CO2. What is more, the probability distributions for this value are quite asymmetric–it is far more likely that if we are wrong, our estimate is too low than that it is too high.

    Then there is the question of what we expect and need from climate models. We do not need to know with any accuracy what the temperature will be on Christmas day 2101. Rather, we need to be able to bound sea level rise and plan for the increase in drought expected. These are more robust results.

    Moreover, even if you were correct that the models were unreliable, do you really think that favors inaction? Would you really rather be landing in a storm, at night without instruments than with instruments telling you that the landing will be difficult?

    Finally, I really wonder where you have been practicing physics if a bit of rough language offends you. Physicists, of all scientific disciplines, are among the most blunt in telling their colleagues precisely what type of organic matter they are full of. You certainly would not have lasted long working with Pauli or Feynmann.

    It is very clear, PAber that you are speaking well outside of your area of expertise. Might I suggest that you not make it a requirement that the voice that is trying to keep you from making an ass of yourself speak to you always in gentle terms.

    Comment by Ray Ladbury — 6 Nov 2012 @ 10:11 AM

  68. “physicist” PAber @~66

    I’m sorry you ran across our outspoken Ray Ladbury, but some slack should be extended to the first responders to climate nonsense. I’ve seen at least one post from you that raised questions about what you know and where you got your information. His work has been consistently reliable despite his acid tongue, or perhaps because of it.

    A google search for you finds this mildly amusing effort about the physics department of Aberstwyth University, but I couldn’t find you.
    http://www.youtube.com/watch?v=oR8mAVTn-Pg

    As the daughter of a physicist (PW Anderson) who refuses to pronounce outside his specialties though he supports real climate science, I note announcing yourself as a physicist is not enough. (Nor, obviously, am I qualified even scientifically despite my familiarity with a whole lot of information, but I do pass the test of mostly not saying things about stuff I don’t know or understand.) There are some sterling examples of rogue physicists such as Freeman Dyson (technocrat), Lubos Motl (string theory), and too long a list of others, pronouncing outside their knowledge. There are also several who have had their words twisted and now have to defend themselves for opinions they don’t even hold, a depressing artifact of the truth-twisting machine.

    I suggest you support your opinions with some more specific information about your experience and qualifications.

    Comment by Susan Anderson — 6 Nov 2012 @ 11:16 AM

  69. Re- Comment by PAber — 6 Nov 2012 @ 2:02 AM:

    You say- “To denigrate someone (anyone?) who disagrees is a clear sign of no other argument.”

    Ray Ladbury may be cranky, but he is a physicist who does know a fair amount about climate models and has expert experience with risk assessment. So how do you feel about someone who accuses a large group of scientists of scientific misconduct without any support whatsoever? On 4 Nov 2012 @ 1:18 AM, you accused scientists of closed minded searching for proof and trying to scare the public for political gain, and don’t wish to explain yourself. Should I assign your strange inexpert accusations to be politically motivated?

    I am wondering how it is political when a large group of scientists, over quite a long period, report data with confidence intervals that provide evidence of potential serious consequences. How do you respond to a group of physicians who tell you that there is some probability of you having a serious condition? How about driving across a bridge or entering a structure that some engineers have condemned on a chance of failure? Are these professionals making political assessments? Steve

    Comment by Steve Fish — 6 Nov 2012 @ 11:16 AM

  70. I find it dismaying to see some of the best minds in climate science, along with some of the best-informed laypersons I have encountered online, bogged down in this thread in arguing with ill-informed and/or dishonest deniers about whether global temperatures are in fact increasing, and similarly bogged down in another thread in arguing about whether sea levels are in fact rising.

    These “arguments” have been long since won, folks. But this is exactly where the fossil fuel interests — who are ultimately the driving force behind all of the denial — want you to be, bogged down in endless arguments over this stuff.

    This is not what the world needs from climate scientists now, or from well-informed and deeply concerned lay people.

    What is needed, instead, is an emphasis on IMPACTS. On sound, scientific attribution of the onslaught of the weather of mass destruction — droughts, floods, heat waves, wildfires and superstorms — that global warming is already bringing down upon us.

    The deniers have already moved on to that — because they know that’s what the public is concerned about now. And the deniers DO NOT WANT YOU TO GO THERE. They want you to go on fighting the battles that you have long since won, about whether global warming is even real, whether any warming has occurred, blah blah blah.

    Because they know that once the public understands that global warming means the collapse of the food supply, and the destruction of cities, that there will, at long last, be an overwhelming demand for action.

    Comment by SecularAnimist — 6 Nov 2012 @ 12:17 PM

  71. @67 [Ray Ladbury]
    1. Of course I am speaking outside my area of expertise. As far as you stick to strict “deep-down” climate studies. Still, this does not mean I can not evaluate the original post and the accompanying figures. Which – together, comprise a self-standing message addressed to? … {well, this is a question I try to answer by looking at the comments…)
    2. While you provided the list of the successes of the models, you have not actually replied to my original point about the figure 4 and the relationship between model results and the observed values. Actually, Gavin was much more honest in answering the issue: the models recreate the observed global temperatures very crudely.

    3. My point was simply that using joined linear trends *requires* some sort of explanation at to the origin of the abrupt change. May I ask: did you try to fit the HADCRUT data with linear and with quadratic formula yourself? Which gives a better fit?
    Once you do this, as yourself: why, instead of immediately opposing it, not to search for mechanisms that change the trend? Each year, each more advanced data gathering programme brings us closer to understanding. I would accept if the data would show this way or that, without looking for excused, in the old tradition of “if the data do not fit the model, so much worse for the data”.

    [Response: This is overly simplistic - data can be misinterpreted or contaminated, comparisons may not be apples with apples, additional unaccounted for effects may be present as well as models being wrong (or incomplete). To think that all apparent mismatches between observations and models must be because the model is wrong is foolish (as would be the converse). Each case is different. In the case of short term trends, one can quickly conclude that they are not predictable without perhaps initialisation of the ocean state at the beginning of the forecast period, and even then, it is very unclear whether there is any skill. They are therefore not a useful guide to the longer term predictions. - gavin]

    4. Of course your points that they recreate other specific phenomena better may be valid. At the moment I have not the time to check all these – so I’ll assume you are right. The problem lies in the communication, not in physics: global temperature increase is one of the AGW hallmark signs, one of the most accessible to the public. I’ll repeat my question to Gavin: are you satisfied with the error bands in hind- and forecast?

    [Response: The 'errors' are related mostly to the spread of single realisations as a function of different paths of the weather. These are not directly predictable beyond a week or so, and statistically, not beyond a a few years (at least experimentally). Is that satisfying? no. Is there much that can be done about it? not really. - gavin]

    5. As for action/inaction – well this is an issue that falls far beyond mere climate model quality. Stupid action may be worse than inaction (in some cases). I am not sure if the proposed (or even imposed) actions, such as carbon credits/trading, are sensible. Or if the efforts/money put into some “green” technologies are, in fact, sensible. The problem lies in such a strong coupling between politics, economy, social movements and science. This has carried the polarization into research: funding feuds, quarrels, nitpicking reviews, accusations. This makes the general public susceptible to propaganda (on both sides!), lies, half-truths etc.
    6. The blogosphere is even more prone to such discord. I am not surprised by the language you have used – I remarked that your post would be better without the last remark. For the very reason that if you really want to convince me it is better to stick to be polite. Of course, I may have gotten your goal of convincing me wrong. In which case the abusive language may have been the right tool.

    Comment by PAber — 6 Nov 2012 @ 12:42 PM

  72. > the spread of single realisations as a function of different paths

    This should be repeated in simpler, clearer words whenever models are discussed.

    Most people, I think, don’t consider that they’re looking at something that is run repeatedly (single realisations, one at a time,) and that runs a bit differently each time (different paths, one at a time) because [help?].

    An example: each pingpong ball falls through the array of pegs in the bell curve demonstrator — each falling pingpong ball is a single realization, follows a single path, and ends up in one bin at the bottom. The result is — exactly — a picture of how error bands work out.

    Here: https://www.google.com/search?q=bell+curve+ball+drop

    Those model a single ball falling.

    Now — imagine how a climate model would look.

    I know this is old obvious stuff to many readers.

    But I am sure it needs to be made clear, repeatedly.
    Gavin’s explained it in words understandable by those who, er, already understand and need to be reminded — or who are using talking points.

    Sincere new readers may need a little more help.

    Comment by Hank Roberts — 6 Nov 2012 @ 3:38 PM

  73. I am wondering if there are two things in front of us that are actually quite linked:

    1. The precipitous decline in Arctic Ice volume that has been described by PIOMAS
    2. The 15 year pause in apparent global temperature

    Inspection of the PIOMAS Yearly Minimum Ice Volume chart shows me that the Arctic ocean has lost approximately 8000 cubic kilometers of volume since 1997. To melt this ice requires about 163 exajoules per year due to the latent heat that gets taken up when that ice is is melted. This 8000 cubic kilometers of ice has gone away and does not comeback each winter. Can the heat energy mopped up by the disappearance of this ice volume account for this 15 year hiatus in warming? (or is 163 exajoules/yr a “drop in the bucket” in global terms?)

    Could it be that the temperature hiatus can be explained by Arctic circulation flows that have been taking the heat north where it has been soaked up as latent heat in this ice phase change? As Arctic ice volume loss, in essence, bottoms out later this decade, will global temperature rise resume “with a vengeance”?

    Comment by Rob Ellis — 6 Nov 2012 @ 4:02 PM

  74. Rob Ellis, you touch on a different question on this issue that I have. When is the cold weather we’ve been getting a kind of Arctic exhalation? The issue I’m reaching for, is when is it a case of cold leaving the Arctic and when more coincidental. I know my phrasing is inelegant and perhaps ambiguous, but I hope somebody can explain the difference between that and the ongoing extremes from the alteration of the jet stream so ably described by Francis et al.

    Secular Animist, I have come to believe that answering the assertions of the likes of PAber are part of the function of RealClimate, unlike the endless nonsense proliferated by the likes of Dan H with his condescending tones that he appears to think hide his outright ignorance and political posturing.

    Comment by Susan Anderson — 6 Nov 2012 @ 5:26 PM

  75. Rob Ellis @73 — Due to natural variability, WMO defines climate as 30 or more years of weather data. Each decade has been warmer than the last since the 1950s.

    Alternatively, consider the statistical analyses done by Tamino in his Open Mind blog, linked on the sidebar.

    Comment by David B. Benson — 6 Nov 2012 @ 7:22 PM

  76. 2. The 15 year pause in apparent global temperature

    The 15-year pause shows up on some the surface air temperature series, but does it make sense versus observations?

    1. sea level rise
    2. sea ice
    3. record high temperatures
    4. ocean heat content

    On Gistemp the 15-year trend is still positive. It remains positive to 11 years. To me that temperature series better agrees with with what is actually happening on the planet.

    Comment by JCH — 6 Nov 2012 @ 10:02 PM

  77. JCH @ 59 – “On Rob’s point about La Nina driving ocean heat to deep layers, that makes sense to me, but I haven’t found much to confirm it on Google Scholar.”

    Perhaps the best illustration of this is in a paper by Roemmich & Dean (2011) – The global ocean imprint of ENSO. Note the upper 700 metres of ocean (60°N-60°S) shown in Figures 3(a) @ (b. During La Nina heat is buried in the subsurface ocean, whereas during El Nino the surface layer is anomalously warm. Note, also, how the globally-averaged sea surface temperature varies in concert with these ENSO phases – warmer with El Nino, cooler with La Nina.

    This is a separate issue to the deep ocean warming in La Nina-like periods suggested by the climate modelling of Meehl (2011). Heat buried in the deep ocean will not re-surface for a very long time.

    Comment by Rob Painting — 7 Nov 2012 @ 2:50 AM

  78. JCH – Note that the colour bar has been left out of Figure 3 in Roemmich & Dean’s paper, but it is the same as that in Figure 2.

    Comment by Rob Painting — 7 Nov 2012 @ 2:58 AM

  79. #74–”I hope somebody can explain the difference between that and the ongoing extremes from the alteration of the jet stream so ably described by Francis et al.”

    I don’t think there is a difference. When the jet stream meanders so far south, it creates an ‘exhalation’ of Arctic air. (We tend to notice this in Georgia, where I live!)

    Comment by Kevin McKinney — 7 Nov 2012 @ 9:38 AM

  80. PAber,
    I’ll admit to being sharp tongued–especially when someone violates a basic tenet of science–to-wit, that the experts are most likely the ones who best understand their field, and the probability of them benefiting from the critiques of neophytes is nil.

    I worked for several years as an editor at a Physics magazine, and countless times, I ran into such prejudices–usually expressed by physicists who worked in nice, clean laboratories and contended that geophysics, oceanography, atmospheric science…(insert your favorite subfield to diss). I actually heard these educated idjits claim these fields “weren’t really physics/science.”

    Now, listen to what I am saying. You are applying the wrong criteria to judging the models. First, the most valuable thing you get from scientific models is not “answers”, but rather insight. Thus, it is a mistake to try to use a model to predict behavior in a single year, or even a single decade. Second, when dealing with a discipline that is inherently concerned with trends, that is the criterion you must apply to the models–do they reproduce the trends more or less properly over the relevant timescales.

    The relevant response to your question about whether one should fit a linear trend, two linear trends with a break or a quadratic is not to be found in figure 4,but rather in figure 2. It is quite easy to break the temperature series into decadal subsets that show no trend–and yet the temperature continues to rise over that entire period. Now it may be that this fact is trying to tell us something very profound–perhaps that once the atmosphere warms to a certain point, there is a hiatus in surface warming, and more heat flows into the deep oceans. And then warming resumes. Moreover, such a “hiatus” does not in any way alter the fact that the surface–or really, the top of Atmosphere must reach a certain temperature before equilibrium is restored. Thus, while interesting, this putative effect does not bear on the issue of whether climate change poses a serious threat.

    As others have pointed out, I am a physicist. My research is very applied, and risk analysis plays a big role in my day job. I am not a climate scientist. I have devoted several years to trying to understand the field, though. And I would point out that countless other physicists and other professional scientists have made similar efforts, and that we have found that climate science holds together pretty well. This validation of the consensus is reflected in the opinions of our professional organizations and of the National Academies of Sciences in dozens of nations. Might I suggest, that if you are not seeing the concordance, perhaps it is because you are being presented with a learning opportunity rather than that you and you alone have found a deep flaw in a field you have devoted virtually no time to understanding.

    Comment by Ray Ladbury — 7 Nov 2012 @ 11:01 AM

  81. Re-comments @ 77 & 78 – the paper is by Dean Roemmich & John Gilson. My bad.

    Comment by Rob Painting — 7 Nov 2012 @ 1:44 PM

  82. Is the following OK?

    1) CO2 (+ some other things) accumulation causes warming.
    2) The rate of CO2 emitted has increased continuously, peicewise linearly with the global economy.
    3) CO2 has accumulated nonlinearly (faster than straight-line).
    4) The effect of accumulated CO2 on temperature is nonlinear (slower than straight-line).
    5) Measured temperature has increased continuously but noisily.

    If thats all true, then:
    6) If CO2 (and others) were halted, so net GHGs were noisily constant, the temperature effect would stabilize? Or the rate of temperature increase would stabilize? I’m trying to get at whether GHGs are proportional to temp change or proportional to rate of temp change.

    7) What is the CO2 accumulation-to-temperature-rise time lag like? e.g, if I converted CO2 to pencils faster than the emmision rate, how long would it take for temperature to trend down? Its not immediate, right?

    I’m working my way through a view that
    8) the globe will not stop increasing GHG emmisions for some decades
    9) but it eventually will when other technology is ready (WAG 2040s)
    10) so the rate of emmision will be lower than now, but the accumulated emmisions will be greater than now.

    I’m trying to decide what happens in my theoretical world if concensus is right. By the IPCC 2007 estimate, temp would be something like 2C higher when my undefined magic tech takes over in the 2040s. How long would it take for temp to stabilize? Does it overshoot?

    Someone here must have modelled that scenario. Advice appreciated.

    Comment by KevinM — 7 Nov 2012 @ 3:18 PM

  83. Kevin (82) – I have tried some statistical modeling of the lag from CO2 increases to temperature increases. There is clearly a long term effect, but there is little or no short term effect. As far as I can tell, there is no noticable effect within six years. Some have found a short-term relationship (some 6-18 months) between temperature and CO2, but this is in the opposite causal direction due to out-gassing from the oceans due to increases in ocean temperature.

    Comment by T Marvell — 7 Nov 2012 @ 8:27 PM

  84. Thanks Marvell. Six years actually seems short for something as big as the planet.

    Is there any literature on the topic?

    I’m also now wondering whether the response for adding CO2 and taking it away should be symmetrical. I’m guessing not, it should take longer for temperature to fall in the absence of a fixed CO2 delta than it takes for it to rise with addition of an equal fixed CO2 delta. The shape of the day-night transitions in average hourly temperature charts for single locations should be a clue.

    In any case you’ve injured one of my other ideas, that global economic activity like a recession should show up in the temperature anomoly series. The latest temp rise slowdown can’t be related to CO2 reduction during the 2007 crisis, because on a cause-delay-effect timescale it has not happened yet (for the thermometers).

    Comment by KevinM — 8 Nov 2012 @ 8:53 AM

  85. Holy cow I just found the earlier post: “The lag between temperature and CO2. (Gore’s got it right.)” where its implied that the time lag I’m looking for could be thousands of years. At various points in the article it was decades (for methane), hundreds of years or thousands of years (for CO2).

    Please clarify.

    In this current article we have rising temperatures caused by added GHG like CO2. Is the rise between 1990 and 2000 primarily due to CO2 from the 1980s or from the 1880s?

    [Response: The time for temperatures to start to respond to increased CO2 is short - you'll see significant changes in a decade or two, even though the full response will be slower. The response of the carbon cycle to changes in temperature (and circulation etc.) is much slower (hundreds of years) and this is what you are seeing in the ice cores. - gavin]

    Comment by KevinM — 8 Nov 2012 @ 9:50 AM

  86. Thanks,

    So temperature increase from 1990 to 2000 would be due to CO2 from 1989, and also from 1889. The answer reads a bit vague but the answer to the ‘primarily’ condition seems to be 10-20 years before, closer to Marvell’s 6 yrs than the older article’s 100s of years. There should be a curve associated with it.

    e.g. for an increment of GHG (like 1 gigaton of CO2) there would be an expected change in final temperature (like 1 degree C – not a real number, but I don’t know the real number). The temperature change would start immediately and settle asymptotically to 1C in a few hundred years.

    Then, a historical net GHG emmissions vs time chart could be made with the GHG types broken into chunks of the reference size. I could substitute a delta-T versus time component for each chunk and answer my question about delays. Would be easy to do in Excel VBA if I had that curve.

    I’m finding older posts and commentary helpful. Have you considered a FAQ page?

    Comment by KevinM — 8 Nov 2012 @ 1:33 PM

  87. Start Here — the FAQ page

    Comment by Hank Roberts — 8 Nov 2012 @ 1:51 PM

  88. KevinM – In regards to what would happen if emissions ceased, you might want to look at the http://www.realclimate.org/index.php/archives/2010/06/climate-change-commitment-ii/ post.

    Comment by KR — 9 Nov 2012 @ 9:00 AM

  89. Thanks KR that article did exactly what I had intended to do. Are any of the preexisting models published? Or at least the major equations that could be put into a C program.

    Another off-the-wall question. The earths core is a lot hotter than its crust. Only a few miles under the ocean, its hot enough to melt rocks. Are there any papers that explain how much of earths heat is internally generated.

    While the earths surface temperatures and oceans should be heating due to GHGs, there should also be some continuous super-long-term cooling happening when you look at the whole mass of the planet. i.e. in enough billions of years it should become a solid. What is the magnitude of the heat transferring from inside to the surface relative to solar radiation?

    Comment by KevinM — 12 Nov 2012 @ 11:48 AM

  90. KevinM@89: I’ll leave others to give pointers to the models — as to heat from the earth’s interior, searching on the words “earth surface heat flux” will probably get you a long way. This is what they produce in Google Scholar, and this first result seems very informative. (This isn’t intended as one of those snippy “let me google that for you” responses, by the way — I recognize that it’s hard to google without knowing the standard terminology for the thing you’re looking for.)

    Interestingly, the heat from the interior of the earth is not just gradual cooling from its time of formation: buried radioactive elements put out a lot of heat. (19th-century cooling-based estimates for the age of the earth were very inaccurate for this reason.)

    Comment by Vilnius — 12 Nov 2012 @ 1:52 PM

  91. Never mind.

    “Total heat loss from the Earth is estimated at 44.2 TW. Mean heat flow is 65 mW/m2 over continental crust and 101 mW/m2 over oceanic crust. This is approximately 1/10,000 of solar irradiation.”

    Forgive my overposting, I’m in a frantic reeducation phase.

    Comment by KevinM — 12 Nov 2012 @ 3:47 PM

  92. KevinM @91 — I strongly recommend Ray Pierrehumbert’s “Principles of Planetary Climate”
    http://geosci.uchicago.edu/~rtp1/PrinciplesPlanetaryClimate/index.html

    Comment by David B. Benson — 12 Nov 2012 @ 7:24 PM

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